In some approaches, an access and mobility management function (AMF) network element serving a terminal may subscribe, according to a requirement, to an event related to the terminal from an event notification network element such as a session management function (SMF) network element, a unified data management (UDM) network element, or a policy control function (PCF) network element. When subscribing to an event, the AMF network element sends a subscription request to the event notification network element. The subscription request carries subscription information, related to the terminal, of the AMF network element, for example, information about a subscription event of the terminal, callback address information, related to the subscription event, of the AMF network element, and a notification correlation identity (ID) allocated by the AMF network element to the subscription event. Further, the event notification network element sends a subscription response to the AMF network element. The subscription response carries a subscription correlation ID allocated by the event notification network element to the subscription event, and the like. In this case, when a notification condition of the subscription event is met, the event notification network element sends, based on the callback address information, related to the terminal, of the AMF network element, an event notification and the notification correlation identity to the AMF network element that has subscribed to the event. The AMF network element correlates the event notification with the subscription event based on the notification correlation identity.
In addition, in some approaches, in a scenario in which a terminal has migrated from a source AMF network element to a target AMF network element, because an event notification network element still stores subscription information, related to the terminal, of the source AMF network element when a notification condition of a subscription event is met, the event notification network element still sends an event notification of the subscription event to a source subscription network element based on the stored subscription information, related to the terminal, of the source AMF network element. As a result, a target subscription network element currently serving the terminal cannot learn the event notification of the subscription event in a timely manner, and therefore cannot process the corresponding subscription event in a timely manner.
Therefore, how to perform a subscription update such that a target subscription network element can learn an event notification of a subscription event in a timely manner in a scenario in which a terminal has migrated from a source subscription network element to the target subscription network element is a problem that needs to be urgently resolved currently.